Electrical connector for welding and riveting



1956 c. F. KURTH ETAL 2,765,395

ELECTRICAL CONNECTOR FOR WELDING AND RIVETING v Filed March 25, 1955 4 Sheets-Sheet l INVENTORS CLARENCE F.KURTH KENNETH D.PURDY 25 ATTORNEY Oct. 2, 1956 c, KURTH r 2,765,395

ELECTRICAL CONNECTOR FOR WELDING AND RIVETING Filed March 25, 1955 4 Sheets-Sheet 2 INVENTORS CLARENCE F.KURTH KENNETH D. PURDY ATTORNEY 1956 c. F. KURTH ETAL ELECTRICAL CONNECTOR FOR WELDING AND RIVETING 4 Sheet s-Sheet 3 Filed March 25, 1955 j 27 m H 28 VIII/I/l/ili lW/l/l/Il;

INVENTORS CLARENCE F.KURTH KENNETH D.PURDY ATTORNEY ocgz, 1956 C. F. KURTH El" AL ELECTRICAL CONNECTOR FOR WELDING AND RIVETING Filed Manch 25, 1955 l I 4 I -l l I 37 37 I i i l 4 Sheets-Sheet 4 INVENTORS CLARENCE F.KURTH KENNETH D.PURDY BY M W ATTORNEY ELECTRICAL CONNECTOR FOR WELDING AND RIVETING Clarence F. Kurth, Wauwatosa, and Kenneth D. Purdy, Milwaukee, Wis., assignors to Allen-Bradley Company, Milwaukee, Wis., a corporation of Wisconsin Application March 25, 1955, Serial No. 496,651

4 Claims. (Cl. 219-158) This invention relates to a self-aligning low-resistance electrical connector for resistance welding, or hot-riveting, a stud or the like to a piece of sheet metal or the like.

More particularly it resides in such a connector in cluding: a main body having a hole with inwardly converging sides; a plurality of wedge-pieces within the hole, each piece having an outer surface fitted to slide on a side of the hole, and an inner surface conforming substantially to the configuration of the stud or the like; resilient means biasing the wedge-pieces apart from each other and outwardly from the hole; stop means carried by the main body to limit the outward movement of the wedge-pieces; and means for conductingly attaching an electric conductor to the main body; the main body and the wedge-pieces being preferably of wear-resting material of high electric conductivity.

The primary use of the above described electrical connector is to serve as one of the two electrodes which conveys current to and through the two pieces of work to be welded or riveted together.

An important feature of the above combination is that, when the stud or the like is subjected to longitudinal pressure, by the pressure of the other electrode thereon (indirectly through the piece of sheet metal or the like in the case of welding, or directly in the case of riveting), the wedge-pieces will present such a large contact-surface to the main body and to the stud or the like that the resistance to the fiow of current from the main body to the stud or the like will be negligible.

A further important feature is that, when such pressure is applied, the stud or the like immediately and automatically becomes axially aligned with respect to the hole, and is firmly gripped in that position by the wedgepieces; and yet, as soon as this pressure is released, .the stud or the like can be readily removed from the connector.

Prior methods of holding and electrically contacting the stud were slow and laborious, and frequently resulted in misaligned studs and defective joints.

Accordingly the principal object of this present invention is to provide a more speedy, more easy, more precise, and more dependable apparatus for performing the desired welding operation.

A further object is to provide apparatus which can equally well be used for speedy, easy, precise, and dependable hot riveting.

Incidental objects are to provide a low-resistance electrical connector, and to provide a gripping device which, in response to longitudinal pressure, toward the device, on the article to be gripped, will immediately and automatically align and firmly grip the article, and yet as soon as this pressure ceases, will release the article.

These and other objects and advantages of this invention will appear in the description to follow. In the description reference is made to the accompanying drawings which form a part hereof, and in which there is shown by way of illustration, and not of limitation, a

nited States Patent specific form in which .this invention may be embodied.

In the drawings:

Fig. 1 is a side elevation of a welding machine including one species of the present invention, which is shown partly in elevation and partly in vertical section. The work is shown before pressure has been applied.

Fig. 2 is an enlarged front elevation, partly in section of the same species, viewed along the line 2-2 of Fig. 1, and as though out along the line 22 of Fig. 3, showing the work with pressure applied but before welding.

Fig. 3 is a horizontal section of the same species, viewed as though cut along the line 33 of Fig. 2. Scale same as Fig. 2.

Fig. 4 is a front elevation of the same species, partly in section, viewed as though cut along the line 4-4 of Fig. 3, showing the work with welding completed and pressure released. Scale same as Figs. 2 and 3.

Fig. 5 is a vertical section of a second species of the invention, shown here as being used for hot-riveting, rather than welding. The work is shown with pressure applied, but before riveting.

Fig. 6 is a somewhat similar section of the second species, taken at right angles to the view of Fig. 5, with the wedge-pieces shown partly in elevation. The work is shown after riveting, and with the pressure released.

Fig. 7 is an elevation of a third species of the invention viewed along the line 77 of Fig. 9, partially in section as though cut along the line 7a7a of Fig. 9.

Fig. 8 is a vertical section of the third species, viewed as though out along the line 8-8 of Fig. 7.

Fig. 9 is a horizontal section of the third species, viewed as though out along the line 99 of Figs. 7 and 8.

Throughout the description, the same reference-number is applied to the same member or to similar members.

Referring now to Figs. 1, 2, 3, and 4, there will first be described the first species of the invention. Although as here shown, the invention is being used for resistance welding, it is to be understood that it can equally well be used for hot-riveting. Compare the second species, hereinafter described.

There is shown in Fig. 1, upper ram 21 and lower ram 22 of a conventional welding-machine, the rest of the machine not being shown. The lower ram is fixed and the upper ram is movable downwardly by the machine under the pressure required for the welding or hot-riveting. The downward movement and retracting of the upper ram, and the turning on and olf of the electrical current are controlled by conventional remote control.

Gripped by an upper horn 23, laterally projecting from upper ram 21, is a conventional upper electrode-holder 24. This electrode-holder is hollow, for the circulation of cooling water through hoses 25.

The electrode 26 has a hat horizontal lower end, wide enough to span the hole 27 in the piece of sheet metal 28 to be welded, so as to afford an ample electrical contact therewith.

Gripped by a laterally projecting lower horn 29 is the lower electrode-holder 30, which is similar to upper electrode-holder 24; but electrode 31 is abbreviated. In the claims lower electrode 31 and its holder 30 are collectively referred to as an electrical conductor.

Electrical current is conveyed to and through the two horns 23 and 29, and the two electrode-holders 24 and 30, in conventional manner.

Everything thus far described is conventional and wellknown in the art.

The main body of the electrical connector which is the subject-matter of the present invention is for convenience made in two parts, 32 and 33.

Now see also Fig. 2. Lower main body 32 is traversed, all the way across, by a vertical slot 34, terminating at its upper edge in a hole 35. Centrally located in the lower main body is a vertical hole 36 slightly larger than electrode-holder 30. This hole is slid down over this elecnode-holder until the main body rests on lower horn 29, and then the main body is clamped to the electrode-holder by tightening screws 37, thus affording a practically resistanceless contact between the electrode-holder and the main body.

Upper main body 33 is secured to lower main body 32 by screws 33, thus affording a practically resistanceless contact between the two parts of the main body.

In the upper part 33 there is a frusto-conical hole 39, in which slide three frusto-conical-sector wedge-pieces 40.

The wedge-pieces and the two parts of the main body should be made of wear-resisting material of high electric conductivity, and some resiliency: for example, Resistance Welder Manufacturers Association Class H Alloy: i. e. chrome copper of about 3% chromium and 97% copper.

Now see also Fig. 3. Three horizontal springs 41 tend to force wedge-pieces apart into close electrical contact with the sides of hole 39, and the resulting pressure be tween hole and wedge-pieces tends to force the wedge pieces upwardly. This upward tendency may be en hanced by a spring 42 which bears upwardly against the bottoms of wedge-pieces and is seated in hole 43 in lower main body 32. Spring 42 may be omitted.

The proper slant of the walls of hole 39 is very important, so as to obtain a proper horizontal component for gripping the stud. This component is derived from the downward motion and force of the upper electrode 26. Also to obtain a proper release of the grip when the pressure of the electrode is relieved. Although the device will operate with other slopes, it has been found in practice that an inclination of to the axis of the hole, is ideal.

Cover-plate 44, attached to upper main body 33 by screws 45, serves to prevent wedge-pieces 40 from being forced any further upwards than the top of hole 3%". Cover-plate 44 has a hole 46, ample for the free insertion of stud 47.

The particular form of the invention just described, is intended for use with studs the main portion of which is essentially cylindrical in shape. Each wedge-piece 40 has an inward projecting ledge 48 designed to fit under some part (such as the bottom) of stud 47, in order to impart downward motion of the stud to the Wedge-pieces, and upward motion vice versa.

The radii of curvature of the inner and outer surfaces of the wedge-pieces will later herein be compared respectively with the radius of curvature of the main cylindrical portion of the stud and the radii of curvature of the hole in which the wedge-pieces slide.

The invention operates as follows. The stud 47 is inserted through hole 46 of cover-plate 44, and between wedge-pieces dil and rests on projections 45 of these wedge-pieces. Notice the space between the stud and the wedge-pieces, and that the wedge-pieces are flush up against cover-plate 44. The operator then holds the pieces of sheet metal 2%, so that neck 49 of the stud projects into hole 27 in the piece of sheet metal.

The whole upper-works is then made to descend. Now see Fig. 2. Head 26 of the upper electrode engages piece sheet metal 23, forcing it down against stud 47, and thus forcing down the stud and hence the wedge-pieces 40. Note now the space between the bottom of cover-plate 44 and the tops of wedge-pieces 4i), and the absence of the space which formerly existed between the wedge-pieces and stud 4-7.

The piece of sheet metal 23 is now definitely horizontal, and stud 4-7 is gripped by the wedge-pieces and is automatically aligned perpendicular to the piece of sheet metal.

And now as to the radii of curvature. The radius of curvature of the inner surface of the wedge-pieces is slightly less than that of the stud. The radius of curva ture of the outer surface at each level of the wedge-pieces is slightly less than that of the inner surface of hole 39 at the corresponding level when the wedge-pieces first grip the stud. Thus each wedge-piece will then have a two-line contact with the stud and a one-line contact with the main body 33.

Tighter gripping of the stud, as it and the wedge-pieces descend very slightly further, will spring each wedgepiece into surface contact with the stud and with the side of hole 39. This results not only in automatically aligning tnc parts for welding but also in providing a low-resistance electrical contact from main body 33 through wedgepieces 4% to stud 47.

If each of the relations of radii of curvature, mentioned earlier herein as less, were instead more, then each wedge-piece would initially have a one-line contact with the stud. and a two-line contact with the main body; but eventually each wedge-piece would still spring into surface contacts. However, the relationship described earlier herein is preferred.

It will be noted that the contact between sheet 28 and stud 47 is a mere circular line where tne lower edge of hole 27 rests on shoulder 5% of the stud. When the current is momentarily on for about a quarter of a second, with everything in the position of Fig. 2, the high resistance at this contact melts the metal and enables sheet 28 to be pressed down into firm contact with the top of the main portion of stud 4 7. The resulting weld is shown in Fig. 4. In that figure, the upper works have been lifted out of contact, the springs have forced wedge-pieces 40 apart and upward, the wedge-pieces contact coverplate 44, and no longer contact the sides of stud &7, which is thus free to be lifted out by lifting sheet 28, to which it is now firmly attached.

The whole operation has consumed only a few seconds, and is practically fool-proof.

Figs. 5 and 6 illustrate a second species of the invention. This species is designed primarily for use with longer studs than the first species. Although, as here shown, the invention is being used for hot-riveting, it is to be understood that it can equally well be used for resistance welding. Compare the other two species.

Only the difierences need be described. In place of the three separate wedge-pieces of the first species, they are all built in one piece. This is a conical-frustum 51, with an extended hollow cylinder 52. To enable the hollow to be bored or cast in this cylinder, the bottom 53 is made in a separate piece, secured to the cylinder 52 in any convenient manner, such as by screws 53a.

Three slots 54, apart, are cut from the top down to nearly the bottom. The natural resiliency of the metal is used, in place of the horizontal springs of the first variant, to spread the three sectors apart and force them upwardly, and spring 42 is seated on top of lower main body 32 instead of in a recess therein.

Neel; 49 of stud 47 is now long enough to project way through hole 27 in sheet 28, so that electrode 2d contacts the top of neck i), instead of contacting shcet Under downward pressure of electrode 26, stud 47 is gripped and aligned by the three pieces of conical frustum 51, as before.

Fig. 5 shows the position -f Neel-i 49 or" stud 47 is hea continued pressure by the ele out on top of sheet Pressre stud is released, and shown in Fig. 6. Sheet 23 a be readily removed.

Figs. 7, 8, and 9 illustrate a third species the invention. This species is designed pi y for use with flat-sided studs, and employs two wedge-pieces, flat-sided, in a fiat-sided hole. Although, as here shown, the invention is being used for resistance welding, it is to be understood that it can equally well be used for hot-riveting. Compare the second species, herein before described.

the p ted, ct

'" inder pressure.

encd, and under is inushroomed then removed, the sumes the position it stud 47, can now The particular form of stud 47, shown in the drawings, has a Greek-cross cross-section.

The main body 55 is in one piece, reinforced by sideplates 56, which confine the two wedge-pieces 57 laterally. The side-plates are secured to the main body by screws 53. At the ends of the top there are two cross-plates 59, which limit the upward movement of the two wedgepieces 57. Above the two cross-plates there is a coverplate 61}. The cross-plates and the cover-plate are secured to main body 55 by screws 61.

Wedge-pieces 57 are forced apart, and hence upwardly, by two parallel horizontal springs 62. There is no vertical spring corresponding to spring 42 of each of the first two species, though such a spring might well be provided here, and omitted there.

Extending across the bottom of each wedge-piece 57 is a rectangular plate 63 which performs the function of inward projection 48 of the first species and bottom-piece 53 of the second species, namely to fit under some part (in this case, the bottom) of stud 47, in order to impart downward motion of the stud to the wedge-pieces, and upward motion vice versa. This plate 63 is attached to the Wedge-pieces by screws 64.

Slot 34, hole 35, and screws 37, function (as shown in the first and second species) to clamp the main body onto the electrical conductor, but in the third species the electrode is of conventional form, and is the part of the conductor onto which the main body is clamped.

The third species operates exactly like the first species.

It will be readily evident from the foregoing description that this invention affords a low-resistance selfaligning electrical connector for resistance-welding, or hot-riveting, having the characteristics prescribed at the beginning of this specification.

Now that three embodiments of the invention have been shown and described and several variations therefrom have been suggested, it is to be understood that the invention is not to be limited to the specific forms or arrangements of parts herein shown and described.

We claim:

1. An electrical connector for resistance-welding or hot-riveting, comprising: a main body, having a hole projecting inwardly from one of the surfaces thereof, with converging sides; a plurality of wedge-pieces within the hole, each having an outer surface conforming substantially to the configuration of a side of the hole, and an inner surface conforming substantially to the configuration of the piece of work to which the connector is to be connected; resilient means, biasing the wedge-pieces apart from each other, and axially outwardly from the hole; stop means carried by the main body for limiting the axial outward movement of the wedge-pieces from the hole; means associated with the wedge-pieces and engageable by the piece of work, for forcing the wedge pieces inwardly lengthwise of the hole whenever the piece of work is forced in that direction; and means for conductingly attaching an electric conductor to the main body; the main body and the wedge-pieces being of wear-resisting resilient material of high electric conductivity; whereby when the piece of work is inserted between the Wedge-pieces, and is subjected to longitudinal pressure inwardly, it will become automatically axially aligned with the hole and firmly gripped by the wedgepieces, and the resistance to the flow of current from the main body to the piece of work, through the wedgepieces, will be negligible; and yet, as soon as this pressure is released, the piece of work can be readily removed.

2. An electrical connector according to claim 1, wherein the hole is a conical frustum; and wherein the configuration of that portion of the piece of work to which the connector is to be connected is cylindrical; and wherein the radius of curvature of the inner surfaces of the wedge-pieces is slightly different than the radius of curvature of the outer surface of said piece of work; and wherein the radius of curvature of the outer surfaces of the wedge-pieces at each level thereof is slightly different (in the same sense) than the radius of curvature of the hole at the corresponding level when the wedgepi-eces first grip said piece of work; for providing tighter gripping of said wedge-pieces to said piece of work, and substantially a surface contact of the Wedge-pieces with the piece of work and with the side of the hole, as the piece of work and the wedge-pieces descend slightly further.

3. An electrical connector according to claim 2, wherein the radius of curvature of the inner surfaces of the wedge-pieces is slightly less than the radius of curvature of the outer surface of the piece of work; and wherein the radius of curvature of the outer surfaces of the Wedge-pieces at each level thereof is slightly less than the radius of curvature of the hole at the corresponding level when the wedge-pieces first grip said piece of work.

4. An electrical connector according to claim 1, wherein the inclination of the converging sides of the hole to the axis thereof is approximately fifteen degrees.

References Cited in the file of this patent UNITED STATES PATENTS 2,371,945 Barbeck Mar. 20, 1945 2,395,228 Lininger Feb. 19, 1946 2,430,237 Moncher Nov. 4, 1947 2,458,928 Brooks Jan. 11, 1949 

